Known methods for transferring a gene into a eukaryote include methods in which a virus vector is used, techniques in which a naked DNA is transferred by endocytosis, electroporation or a gene gun, and the like. The virus vectors are utilized in the filed of gene therapy for broad applications including basic and clinical ones. For example, adenovirus vectors are suitable for transient expression of a gene of interest in a target cell in large quantities. Retrovirus vectors can be used for long-term stable expression due to the function of stable integration into a host chromosome. It is expected that the vector can be used in the field of gene therapy of a genetic disease, or in the field of transgenic animal production. However, since the retrovirus vector results in gene transfer through viral infection, the tropism of the virus raises a problem. Gene transfer does not occur if the cell does not express a receptor on the cell surface. For overcoming this problem, efforts have been made to alter the host range by pseudotyping through modification of an envelope of a retrovirus vector, or to increase the titer. The pseudotyping of a retrovirus vector is mainly achieved by substituting an envelope protein derived from another virus species for an envelope protein in a conventional retrovirus vector (e.g., a vector derived from murine leukemia virus). For example, a retrovirus vector in which vesicular stomatitis virus envelope glycoprotein VSV-G is utilized to infect broad range of hosts (Patent Document 1, Non-patent Document 1), and a vector in which gibbon ape leukemia virus (GaLV) envelope is utilized to increase the efficiency of transfer into human hematopoietic stem cells (Patent Document 2, Non-patent Document 2) have been developed.
Aiming to modify only sugar chain modification of an envelope, which is a glycoprotein, without altering the amino acid sequence of the envelope protein, a technique in which α(1,3)galactosyl epitope on the surface of a retrovirus is decreased for preventing inactivation of the retrovirus vector by humoral components has been examined (Patent Document 3). Disruption of a galactosyltransferase gene in a retrovirus producer cell, utilization of an inhibitor of sugar chain synthesis, utilization of a sugar chain-degrading enzyme and the like are proposed therein. However, gene disruption requires a complicated procedure, and it is necessary to determine suitable conditions for using the inhibitor of sugar chain synthesis or the sugar chain-degrading enzyme.
An N-acetylglucosaminyltransferase III (GnT-III) is an enzyme that transfers a bisecting N-acetylglucosamine (GlcNAc) residue to an N-linked sugar chain on a glycoprotein. GnT-III-encoding genes have been cloned from rat and human (Non-patent Document 3, Non-patent Document 4).
It has been reported that when a GnT-III gene is transferred into a cell infected with hepatitis B virus, production of the virus is inhibited because of suppression of viral gene expression (Non-patent Document 5). Regarding retroviruses, the influence of GnT-III on virus production or the infection efficiency of the produced virus is unknown.
Patent Document 1: WO 94/29440
Patent Document 2: WO 94/23048
Patent Document 3: WO 96/03520
Non-patent Document 1: J. C. Burns et al., Proc. Natl. Acad. Sci. USA, 90:8033-8037 (1993)
Non-patent Document 2: A. D. Miller et al., J. Virol. 65:2220-2224 (1991)
Non-patent Document 3: A. Nishikawa et al., J. Biol. Chem., 267:18199-18204 (1992)
Non-patent Document 4: Y. Ihara et al., J. Biochem., 113:692-698 (1993)
Non-patent Document 5: E. Miyoshi et al., J. Biol. Chem., 270:28311-28315 (1995)